1. Field of the Invention
This invention relates to a head mounted display (HMD) mounted on an observer""s head or face for displaying the character information of an image.
2. Related Background Art
In recent years, with the downsizing and lighter weight of pocketable telephones and personal digital assistant (PDA) or the like having electronic mail and scheduler functions, the concept of wearable computing such as mounting or always carrying these devices on one""s clothes or body is taking root.
As a display device used in this wearable computing, attention has been paid to a head mounted display heretofore used as the display of package video or virtual reality (VR), and various computer systems utilizing the same have been proposed as shown in Japanese Patent Application Laid-Open No. 10-289034.
As head mounted displays utilized in the wearable computing, there are a display A of a type as shown in FIG. 1A of the accompanying drawings wherein the main body of a display unit is fixed through a belt, and a display B which, as shown in FIG. 1B of the accompanying drawings, is hung on the ears through bows 2 attached to the main body 1 of a display unit, and use is made of displays having various functions and in various forms conforming to places and situations. Also, the display B shown in FIG. 1B can be contained by the bows 2 provided on the sides of the main body 1 of the display unit being bent in the directions of the arrows through hinges 3.
FIG. 1C of the accompanying drawings shows the construction of a head mounted display according to the prior art using a compact and light-weight liquid crystal panel as a display element, and the output of a decoder processing unit 11 for inputting a video signal and the output of a power supply circuit 13 having a power supply switch 12 connected thereto are connected to a display drive circuit 14. Also, the outputs of the power supply circuit 13 are connected to illuminating back lights 16L and 16R through drivers 15L and 15R, respectively, and the outputs of the display drive circuit 14 are connected to display elements 17L and 17R for left and right eyes comprising liquid crystal panels which do not emit light by themselves. Optical elements 18L and 18R each comprising a prism are attached to these display elements 17L and 17R, respectively, and the optical elements 18L and 18R are formed with incidence surfaces 18La, 18Ra, reflecting surfaces 1BLb, 18Rb and half mirror surfaces 18Lc, 18Rc, respectively. Display optical systems 19L and 19R are formed by the left and right drivers 15L and 15R, back lights 16L and 16R, display elements 17L and 17R and optical elements 18L and 18R, respectively.
When the power supply switch 12 is closed, the power supply circuit 13 starts the supply of electric power necessary to the entire image display. An NTSC signal which is a video signal from a TV tuner or a video reproducer is inputted to the decoder processing unit 11 and converted into an RGB signal, whereafter it is outputted to the display drive circuit 14, and images are displayed on the display elements 17L and 17R. Also, the display elements 17L and 17R are not self-light emitting type elements and therefore are illuminated by the illuminating back lights 16L and 16R, respectively.
In the display optical systems 19L and 19R, beams emitted from the back lights 16L and 16R and passed through the display elements 17L and 17R are incident on the incidence surfaces 18La and 18Ra of the optical elements 18L and 18R, respectively, and are further incident on the reflecting surfaces 18Lb and 18Rb at an angle of incidence equal to or greater than a critical angle and are totally reflected. These totally reflected beams are reflected by the half mirror surfaces 18Lc and 18Rc, and are again incident on the reflecting surfaces 18Lb and 18Rb at an angle of incidence smaller than the critical angle, and are images on an observer""s pupils eL and eR (of which eR is not shown). As the result, the images displayed on the display elements 17L and 17R are enlargedly observed by the observer.
The above-described head mounted display according to the prior art, however, does not take it into consideration to carry the head mounted display to the outdoors in order to perform mobile computing or wearable computing, and is of a shape unsuitable for carrying. Accordingly, it is more preferable that the head mounted display be mounted on the head only when electric mail is to be read or when access is to be had to the internet, and can be dismounted from the head and contained and carried in a bag or the like when the access or the like is completed. Further, the head mounted display according to the prior art is not designed to be capable of more simply controlling an external apparatus.
It is a primary object of the present invention to provide a head mounted display which is easy to carry in its daily used state and is easy to mount and dismount.
It is another object of the present invention to provide a head mounted display which can be utilized for a long time with the amount of use of a battery curtailed and without the battery being recharged, and a control method of making it possible.
It is still another object of the present invention to provide a head mounted display which makes an external apparatus connected thereto more simply controllable, a control method and a control program for a video signal supplying apparatus which make it possible.
Other objects of the present invention will become apparent from the following description of some embodiments of the invention.